The present invention relates to a method of manufacturing a solid electrolytic capacitor having a high polymer solid electrolyte, and an apparatus of manufacturing the same.
In the recent trend of higher frequency in power source circuits of electronic appliances, electrolytic capacitors used in such electronic appliances are demanded to have an excellent high frequency characteristic. To meet this demand, in order to realize low impedance in high frequency region, a solid electrolytic capacitor using conductive high polymer having a high conductivity obtained by electrolytic polymerization as solid electrolyte is being proposed.
In a method of manufacturing a solid electrolytic capacitor using conductive high polymer as solid electrolyte, as a method of forming a conductive high polymer film on an anodic forming film (dielectric) having an electric insulator, it is proposed to develop a method of forming a conductive high polymer film comprising a step of forming a metal oxide (for example, manganese dioxide) formed on an anodic forming film or a conductive high polymer film (for example, conductive high polymer film having pyrrole chemically oxidized by ammonium persulfate) formed by chemical oxidation polymerization as a conductive layer, and a step of feeding current to this conductive layer to perform electrolytic polymerization.
However, in order to form a high polymer film by electrolytic polymerization simultaneously in the individual capacitor elements of a plurality of capacitor elements, the following method is required. That is, as shown in FIG. 10, in an electrolytic solution 6 containing monomer such as pyrrole and support electrolyte (hereinafter called polymerization solution), each anode electrode 8 having a valve metal and each current feeding electrode 9 (hereinafter called polymerization electrode) contact with each other. Using this polymerization electrode 9 as the positive electrode, voltage is applied between the polymerization electrode 9 and cathode 10, and electrolytic polymerization is performed. In this case, the polymerization electrode 9 contacts directly with the conductive layer on the anodic forming film of the anode electrode 8 of valve metal.
However, the conventional manufacturing method of solid electrolytic capacitor requires complicated steps such as a step of preparing one polymerization electrode 9 for one capacitor element, and a step of contacting between one polymerization electrode and one anode electrode 8 of valve metal. It is hence difficult to mass-produce efficiently.
Besides, when the polymerization electrode 9 contacts with the conductive layer on the anodic forming film of the anode electrode 8, the anodic forming film may be injured to cause a defective part. This defective part may contact with the conductive high polymer film used as the cathode. Accordingly, the product manufactured by this method may have a large leak current and a low withstand voltage. In the conventional method, hence, it was difficult to obtain a capacitor element for realizing a solid electrolytic capacitor of high reliability.
Yet, when assembling a solid electrolytic capacitor by using a capacitor element manufactured by this conventional method, it is required to join independent terminal members (not shown) individually to the anode and cathode (not shown) formed on the capacitor element, and cover with external resin (not shown). It hence involves many problems in the assembling precision and the number of assembling steps.
It is therefore an object of the invention to present a method of manufacturing a solid electrolytic capacitor having excellent characteristics, superior reliability, and outstanding mass producibility, and an apparatus of manufacturing the same.
A manufacturing method of solid electrolytic capacitor of the invention comprises:
(a) a step of supplying a band metal having a central part in the width direction and a plurality of protrusions formed at an end part in the width direction,
(b) a step of forming a dielectric layer on the surface of the plurality of protrusions,
(c) a step of adhering a conductive tape to the central part,
(d) a step of forming a conductive high polymer film above the plurality of protrusions, by performing electrolytic polymerization by starting polymerization from the conductive tape,
(e) a step of peeling the conductive tape from the metal, and
(f) a step of fabricating a plurality of capacitor elements by cutting off individual protrusions from the plurality of protrusions, from the band metal forming the conductive high polymer film.
Preferably, the invention further comprises:
(g) a step of placing a conductor layer above the dielectric layer, in which the conductive high polymer film is formed on the conductor layer.
Preferably, the step of forming the conductive high polymer film includes a step of polymerizing the conductive high polymer film on the conductor layer electrolytically, by using the conductive tape as a common positive electrode, and using electrodes connected to the individual power sources as individual independent negative electrodes.
Preferably, the invention includes at least one of the following steps:
(h) a step of laminating each capacitor element of the plurality of capacitor elements at a specified position of a band metal lead frame having a plurality of pairs of terminal parts,
(i) a step of connecting each pair of terminals of the plurality of pairs of terminals electrically to the anode lead-out part and cathode lead-out part respectively,
(j) a step of covering the laminated capacitor elements with an external resin, and
(k) a step of fabricating individual solid electrolytic capacitors by cutting off the pair of terminal parts having the covered capacitor elements, from the metal lead frame.
Preferably, the step of supplying the band metal includes a step of adhering an electric insulating tape to the central part, forming an anode lead-out part at the central part side, and forming a cathode lead-out part on the protrusions,
the anode lead-out part and cathode lead-out part are electrically insulated by the electric insulating tape,
the conductive tape is adhered on the electric insulating tape, and
the conductive high polymer film is formed on the cathode lead-out part.
A manufacturing apparatus of solid electrolytic capacitor of the invention comprises:
(a) a band metal supply unit for supplying a band metal having a central part, and a plurality of protrusions formed at least at one side edge of both side edges positioned at both sides of the central part,
(b) a dielectric forming unit for forming a dielectric layer on the surface of the plurality of protrusions,
(c) a conductor forming unit for forming a conductor layer on the dielectric layer,
(d) a conductive tape adhering unit for adhering a conductive tape to the central part,
(e) an electrolytic polymerization unit for forming a conductive high polymer film above the plurality of conductive layers, by performing electrolytic polymerization by starting polymerization from the conductive tape,
(f) a conductive tape peeling unit for peeling the conductive tape from the metal, and
(g) an element cutting unit for fabricating a plurality of capacitor elements, by cutting off individual protrusions from the plurality of protrusions, from the band metal forming the conductive high polymer film.
Preferably, the band metal supply unit includes a slit forming unit for forming a plurality of protrusions by forming a plurality of slits at specified intervals in the end part in the width direction of the band metal.
Preferably, the invention comprises at least one element of the following constituent elements:
(h) a laminating unit for laminating individual capacitor elements of the plurality of capacitor elements at specified positions of a band metal lead frame having a plurality of pairs of terminal parts,
(i) a connecting unit for connecting terminals of each pair of the plurality of pairs of terminals electrically to the capacitor elements,
(j) a forming unit for covering the laminated capacitor elements with an external resin, and
(k) a product dividing unit for fabricating individual solid electrolytic capacitors by cutting off the pair of terminal parts having the covered capacitor elements from the metal lead frame.
According to such manufacturing method and manufacturing apparatus, it is easy to work in the steps from forming treatment to electrolytic polymerization for manufacturing a plurality of capacitor elements continuously, and the mass producibility notably enhanced. Moreover, it prevents occurrence of defective part due to injury of the anode foil. Therefore, occurrence of defective part in the conductive high polymer film is prevented. As a result, the invention provides a capacitor element for solid electrolytic capacitor having excellent performances, such as a small leak current, high withstand voltage, and excellent reliability.
The process from the step of laminating a plurality of capacitor elements on a band metal lead frame forming and having terminals to the step of covering these laminated matters with an external resin can be done continuously by using the band metal lead frame. Accordingly, the solid electrolytic capacitor having an excellent assembling precision and a high reliability can be manufactured efficiently.